Stable hydrocarbon lubricating oils and process for forming same

ABSTRACT

HYDROCARBON LUBRICATING OIL RESISTANT TO DETERIORATION UPON EXPOSURE TO LIGHT AND AIR IS FORMED BY CONTACTING SELECTED HIGH BOILING HYDROCARBONS WITH A HYDROCRACKING CATALYST AND HYDROGEN, SEPARATING A LUBRICATING OIL FRACTION FROM THE PRODUCT AND EXTRACTING THE FRACTION IN MULTIPLE STAGE WITH A SOLVENT SELECTIVE FOR CYCLIC HYDROCARBONS.

United States Patent US. Cl. 208-96 8 Claims ABSTRACT OF THE DISCLOSURE Hydrocarbon lubricating oil resistant to deterioration upon exposure to light and air is formed by contacting selected high boiling hydrocarbons with a hydrocracking catalyst and hydrogen, separating a lubricating oil fraction from the product and extracting the fraction in multiple stages with a solvent selective for cyclic hydrocarbons.

RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 616,197, filed Feb. 15, 1967 now abandoned.

FIELD OF THE INVENTION This invention has to do with stable hydrocarbon lubricating oils which are resistant to deterioration upon exposure to light and air, and to a process and means for obtaining the same.

DESCRIPTION OF THE PRIOR ART For many years, lubricating oils have been obtained from hydrocarbon oils of various character by fractional distillation. In order to obtain lubricants of relatively high viscosity index (V.I.), it has been the practice to subject the oils to solvent extraction to remove components serving to lower the V.I. The solvent extracted lubricants are resistant to light and air; however, they are generally fortified with one or more additives in order to improve their resistance during use to oxidation and the like.

More recently, hydrocarbon lubricating oils of somewhat ditferent character have been obtained by a variety of processes in which high boiling fractions are contacted with hydrogen in the presence of hydrocracking catalysts at elevated temperatures and pressures. Lubricating oil fractions are separated from the resulting products. Such lubricating oil fractions differ from those obtained by fractional distillation of crude oils and the like, since they have such relatively high V.I. values that solvent extraction treatments are generally not required to enhance their V.I. values. However, such lubricating oil fractions sulfer from the shortcoming that they are unstable when exposed to light (particularly, actinic rays) and air. When so exposed, sediment and lacquer formation occurs, thus lessening the commercial value of such lubricants. The present invention is directed to a process and means for overcoming such a shortcoming.

It has been proposed hitherto, for example, to subject a partially deasphalted oil to a relatively mild hydrogen treatment, rather than a rigorous hydrocracking, to convert up to about 20 volume percent of the oil to a lubricating oil fraction of relatively low viscosity index. Thereafter, the lubricating oil fraction is extracted conventionice ally wilth a selective solvent to extract at least about 20 volume percent of the lubricating oil fraction and to obtain a rafiinate having a viscosity index of about 95. In conventional solvent extraction of lubricating oil fractions, from about 20 to about volume percent of the fraction is extracted.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a process and means for forming lubricating oils resistant to deterioration upon exposure to light and air. There are also provided the stable oils so formed.

The process of the present invention comprises contacting a selected high boiling hydrocarbon fraction with a hydrocracking catalyst in the presence of hydrogen at elevated temperature and at elevated pressure to convert said fraction to a product containing from about 25 to about 50 volume percent of components boiling below about 650 F., said product comprising a plurality of fractions including a lubricating oil fraction boiling above about 650 F. and having a viscosity index of at least about 110. The lubricating oil fraction is separated from the product. The lubricating oil fraction is then extracted in a plurality of stages with a solvent selective for cyclic hydrocarbons, to form a raffinate having a viscosity index substantially the same as the viscosity index of the lubricating oil fraction, and an extract. The extract comprises from about 0.5 to about 10 volume percent of the components of the lubricating oil fraction. Solvent is then removed from said raffinate.

DESCRIPTION OF SPECIFIC EMBODIMENTS Hydrocarbon feed fractions The hydrocarbon feed material or fraction 'which can be contacted with hydrogen as described herein, has a boiling range above about 650 F. Such materials are selected from heavy gas oils, residual stocks, cycle stocks, topped crudes bright stocks (e.g. substantially deasphalted raffinates) and mixtures thereof. These materials can be obtained by fractionation, as by vacuum distillation, of crude oils identified by their source, viz: Pennsylvania, Mid-Continent, Gulf Coast, West Texas, Amal, Kuwait and Barco.

Hydrocracking catalysts The catalysts employed herein can include any type of hydrocracking catalyst. Such catalysts have hydrogenation and dehydrogenation, and cracking properties, and are well known in the art. The catalysts include oxides and sulfides of any metal of Group VIA of Mendeleelfs Periodic Table, or mixture thereof, typical of which are: chromium sulfide, molybdenum sulfide and tungsten sulfide. Others include oxides and sulfides of Group VIII of said Periodic Table or mixture thereof, as illustrated by: the sulfides of iron, cobalt, nickel, palladium, platinum, rhodium, osmium and iridium. Still other catalysts include mixtures of the above oxides and sulfides of the metals of Group VIA and VIII of said Periodic Table,

3 Additional preferred catalysts include a sulfided or unsulfided 1-8 weight percent cobalt oxide and 3*2O weight percent molybdenum trioxide on a silica-alumina or silica-zirconia base containing silica in amounts of from about 5 to about 95 weight percent.

Catalysts comprised of such metals associated with molecular sieves can also be employed. Such catalysts are typified by those described in US. Pat. No. 3,173,- 854.

The catalyst after use loses some of its activity and, therefore, is regenerated. The spent catalyst is contacted with a free oxygen-containing atmosphere at an elevated temperature sufiicient to burn carbonaceous deposits from the catalyst. Conditions for regenerating the catalyst include a temperature between about 600 F. and about 1000" F., a pressure of from atmospheric to about 500 pounds per square inch, a total gas flow rate of from about 1 to about 20 volumes per volume of catalyst per minute and an oxygen concentration of from about 0.1 percent to 100 percent. The oxygen can be diluted with steam, nitrogen or other inert gas.

Hydrogen Pure hydrogen can be used. However, hydrogen of low purity obtained by recycle or other hydrogenating process can be used, but it is recommended that the recycle hydrogen be subjected to purification to remove some of the undesirable impurities such as water, sulfur compounds, methane and the like. The hydrogen can be circulated at a rate in the range of from about 1000 to about 20,000 standard cubic feet (s.c.f.) per barrel of hydrocarbon charge, and preferably 5000,000 s.c.f. per barrel of charge. Generally, there is a hydrogen consumption of at least about 500 s.c.f. per barrel of charge.

Hydrogen contact operation Hydrocarbon charge is contacted with hydrogen and a catalyst of the character described above, at a temperature ranging from about 500 F. to about 1000 F., preferably 600850 F. Hydrogen pressure is of the order of from about 1000' to 10,000 pounds per square inch gauge (p.s.i.g.). Liquid hourly space velocity (LHSV) of charge normally falls within the range of 0.1 to 10, preferably 0.2-2, volumes of charge (as 60 F. liquid) per volume of catalyst per hour.

The hydrogen contact can be carried out in any suitable equipment for catalytic operations. The contact can be operated batchwise. It is preferable, however, and generally more feasible to operate continuously. Accordingly, the process is adapted for operations using a fixed bed of catalyst. The process can be operated using a moving bed of catalyst wherein the hydrocarbon flow can be concurrent or countercurrent to the catalyst flow. A fluid type of operation wherein the catalyst is carried in suspension in the hydrocarbon charge can be employed.

In the contact with hydrogen, reaction conditions of temperature, pressure, space velocity and type of catalyst are controlled to effect conversion of the hydrocarbon charge and to produce lubricants having a V.I. of about 110 and greater. Conversions vary between about 25 percent and about 50 percent by volume to products boiling lower than about 650 F. Preferably, conversion is about 30 percent for the production of lubricating oil fractions having a V.I. of approximately 110, and about 40-45 percent for 120 V1. and higher lubricating oil fractions.

H product fractionation Following the hydrogen contact, products are withdrawn from a suitable reactor and are then passed through a heat exchanger or other suitable cooling device, wherein they are cooled to temperatures at which hydrogen gas can be separated. The cooled eflluent is then passed into gas separators. Gases are removed and 4 liquid product is passed to a fractionator from which several fractions are removed. A lubricating oil fraction boiling above about 650 F. constitutes one of such fractions.

The lubricating oil fraction may contain some wax products. Removal of wax, if present, can be accomplished by any treatment conventionally used for dewaxing oils to provide an oil having a pour point below about 20 F. or lower. Such dewaxing can be completed at this stage of the process or following solvent extraction described below.

Solvent extraction As indicated above, solvents employed for extraction of the lubricating oil fractions are those having selectivity for cyclic hydrocarbons, including aromatics and fully and partially hydrogenated aromatics. Solvents of this character are well known in the art, being typified by furfural, liquid sulfur dioxide, mixtures of liquid sulfur dioxide and benzene, nitrobenzene, phenol and beta, beta dichloroethyl ether (Chlorex). Particularly preferred herein is furfural.

It has been determined that the volume of solvent should range from about 30 to about 200 percent by volume of solvent per volume of lubricating oil fraction. Surprisingly, a single stage extraction with 200 percent of a solvent such as furfural at 180 F. or at 250 F. is inadequate for the production of a stable lubricating oil. It is essential that a multistage extraction be employed, preferably at least three stages, with the volume of solvent being of the range specified above. Particularly advan tageous results have been realized by employing a fivestage extraction with furfural.

Temperature employed for the solvent extraction varies with the solvent which is selected. By way of illustration, furfural (boiling point, 323 F.) is employed at temperatures of the order of from about F. to about 250 F., preferably about 180 F.

In contrast to conventional solvent extraction of lubricating oil fractions distilled from crude oils, wherein extracts comprise from about 20 to about 60 volume percent of the fractions, the extent of the extraction is considerably less severe. With the quantities of solvent and temperatures selected, approximately from about 0.5 to about 10 percent by volume of the components of the lubricating oil fraction are removed by the solvent and are present in the resulting extract phase. Accordingly, the severity of the solvent extraction herein is controlled such that not more than about 10, and preferably not more than about 5, percent by volume of the lubricating oil fraction is separated in the form of an extract. Thus, the raffinate constitutes about 99.5-90, and preferably more than about 95, percent by volume of the fraction so treated with the solvent.

Solvent present in the rafiinate phase obtained by extraction is readily removed therefrom by distillation. The solvent-free rafiinate constitutes the desired stable lubricating oil fraction.

Multistage solvent extraction can be accomplished in a suitable tower, or with a plurality of mixers and settlers, or any other conventional equipment. By way of illustration multistage extraction can be conducted in the manner described in US. Pat. Nos. 2,022,259 and 2,121,325 wherein a plurality of mixers and settlers are shown, and in US. Pat. No. 2,865,852 wherein a suitable tower operation is shown.

When the lubricating oil fraction which is extracted with solvent contains some wax, the character of the wax is also improved by the solvent extraction. That is, components deleterious to the wax are removed with the solvent extract.

ILLUSTRATIVE EXAMPLES The following examples illustrate, and in no sense, limit the invention.

Example 1 A Kuwait-Barco propane deasphalted raffinate was treated with hydrogen as described below. The charge stock had the following properties:

Gravity, API 22.4 Vacuum assay, F.:

IBP 637 70% 1136 Viscosity index 85 Viscosity at 210 F.:

Kinematic viscosity, cs. 34.34 Saybolt seconds Universal 162 Four Point, F. 115 Flash Point, F. 606 Carbon residue, Weight percent 1.09 Nitrogen, weight percent 0.08 Sulfur, weight percent 193 Temperature, F 772 Pressure, p.s.i.g 2000 LHSV 0.8 H circulation, s.c.f./bbl. 8000 Conversion (100-products boiling above 650 in volume percent 43 0.4. fresh charge and 0.4 liquid recycle, 400650 F. fraction.

The catalyst comprised a silica-zirconia support containing approximately 11 percent by weight of Zr The support was then spray impregnated with 10 percent M00 as a water solution of ammonium molybdate, (NHQ MO7O24.4H2O, drying at 220 F. for 16 hours and calcined for 3 hours at 1000 F. in air. The resulting composite was then impregnated with 3 percent C00 as a water-solution of cobalt nitrate, Co(NO .6H O, dried at 230 F. for 3 hours and calcined 10 hours at 1000 F. in air. The resulting catalyst was sulfided with a 50 percent H -50% H 8 mixture employing 2 volumes per volume of catalyst per minute for hours at 800 F. Further details of the preparation and character of this catalyst are available in US. Pat. 3,182,012, issued May 4, 1965.

The liquid product obtained by contact with hydrogen and the catalyst Was fractionated, thereby providing approximately 57 percent by volume of a lubricating oil fraction having a boiling point above about 650 F.

The lubricating fraction was then dewaxed at about 0 F., with 3 volumes of 50/ 50 (volume) methyl ethyl ketone (MEK) /toluene. The dewaxed oil thus obtained had the following properties:

API Gravity, 60 F 34.0 Vacuum Assay at 10 mm., F. Vol. percent at 760 mm.

IBP 627 5% 780 10% 813 30% s 891 50% 958 70% 1026 Viscosity Index 131 Viscosity at 210 F. SSU 57.2 Pour Point, F. Flash Point, F. 470 Carbon residue, Conradson 0.03 Nitrogen, p.p.m 2 Sulfur, wt. percent 009- Color, ASTM -3 6.0

The dewaxed oil was contacted in a batch mixersettler, employing a five-stage extraction with equal amounts of the oil and furfural. The total quantity of furfural was 100 percent by volume of the dewaxed oil. Extraction temperature was 180 F. The raffinate and extract phases were nitrogen stripped, then vacuum distilled at a maximum temperature of about 285 R, whereupon furfural was removed therefrom. The resulting extract comprised about 2 percent by volume and the raf finate 98 percent by volume. The rafiinate has a viscosity index of 132.

The dewaxed lubricating oil fraction before extraction with furfural, formed sediment and lacquer upon exposure to air and an ultraviolet light source for less than 24 hours. The furfural-extracted dewaxed oil (furfuralfree rafiinate) formed no sediment or lacquer when exposed to the same light source for more than 970 hours. The ultraviolet light test used on the oil fractions was conducted in accordance with ASTM Test Method D 529, Cycle A With an operating temperature of approximately F. and a Xenon lamp. Samples of the oil fractions were contained in 4 dram glass vials during the test.

Example 2 When another portion of the dewaxed oil was extracted with furfural under the same conditions, except for the use of only 50 volume percent of furfural, the extract comprised 1 percent by volume and the raffinate 99 percent by volume. The furfural-free rafiinate, which has a viscosity index of 133, was free from sediment and lacquer formation after more than 890 hours of exposure to the same light source.

The character of the lubricating oil products of Examples 1 and 2 are shown in Table I following. In addition to the ultraviolet light test, the oil products were exposed to sunlight by adding sufficient oil to fill about one-half of a four (4) ounce, tall-form bottle, and placing the bottle on a window sill having a southern exposure.

TAB LE I Example 1 Example 2 Furfural treating conditions:

Stages 5 5 Furiural, percent vol 100 50 Temperature, F 180 180 Yield ratfinate, percent vo1., by gravity balance 98 99 Charge stock PropertiesRaflinate:

Gravity. API 34. 0 34. 3 34. 1 Sp 60 F. (PYC) 0.8550 0.8536 0. 8543 Pour Point, F 20 20 20 SSU at 100, F 307.6 316. 5 313 SSU at 210, F 57. 2 57. 9 57. 7 Viscosity Index. 131 132 133 Color, ASTM Dl500-l L6. 0 L1. 5 L2. 0 Aromatic content, percent wt... 14. 5 13. 4 Stability:

ASTM D529 24 970 890 Windowsill exposure, days 1 30 Extract, yield, percent vol.: 2 1 Gravity, API 22. 7 17. 8 Gravity, Sp. at 60 F. (PYC) 0. 9175 0. 9477 Example 3 A waxy 650 F.+bottoms obtained by contacting a Kuwait-Barco raffinate at 840 F., 0.4 LHSV, 2000 p.s.i.g. H pressure, and 8000 s.c.f./bbl. H circulation, with a catalyst of the character described in Example 1, was employed. This material was treated with furfural at 180 F. with 150 percent by volume of furfural in a five-stage extraction. The resulting extract comprised about 8 percent by volume. The waxy furfural raflinate so obtained constituted 92 percent by volume. It was then dewaxed with 60/40 MEK/toluene, to a 20 F. pour point.

The dewaxed oil product was tested in the ultraviolet light test. The oil was found to be stable during 494 hours of exposure, with no formation of sediment or lacquer. Another portion of the oil was subjected to the windowsill test; no evidence of instability was found during 110 days of exposure.

Example 4 A portion of the waxy 650 F.+bottoms described in Example 3, was treated with furfural at 180 F. with 100 percent by volume of furfural in a three-stage extraction. The resulting extract comprised about 1 percent by volume. The resulting waxy furfural rafiinate comprised 99 percent by volume. The rafiinate was then dewaxed with 60/40 MEK/toluene, to a 20 F. pour point. The dewaxed oil product had a color of L 1.5.

The dewaxed oil product was stable in the ultraviolet light test for about 255 hours.

Example 5 A Mid-Continent heavy vacuum gas oil of the following character was employed:

Nickel, parts per million (p.p.m.) 0.01 Vanadium, parts per million (p.p.m.) 0.4

This gas oil was treated with hydrogen as described below:

Temperature, F. 790 Pressure, p.s.i.g 2000 LHSV 0.8 H circulation, s.c.f./bbl. 800

0.4 fresh charge and 0.4 liquid recycle, 100-650 F. fraction.

The catalyst used was a fresh portion of the catalyst described in Example 1, above.

The liquid product obtained by so hydrocracking the heavy gas oil was fractioned. A waxy lubricating oil fraction boiling above about 650 F., comprised 60 percent by volume, and had a V.I. of 129 (dewaxed to 20 F.

pour point).

The waxy lubricating oil fraction was then contacted in a batch mixer-settler, using a five-stage extraction with equal amounts of the oil and furfural. The total quantity of furfural was 100 percent by volume of the lubricating oil fraction. Extraction temperature Was 180 The resulting raffinate and extract phases were processed as described in Example 1.

The resulting extract comprised about 5.2 percent by volume, and the raifinate about 94.8 percent by volume. The rafiinate contains wax and has the following properties Gravity, API 34.7 Viscosity K.V. at 210 F., cs 6.01 SSU at 210 F. 45.9

Pour Point, F 115 Color, ASTM D 1500-1 1 The rafiinate was then dewaxed at about 0 F., with 3 volumes of 50/50 (volume) methyl ethyl ketone (MEK) /toluene. The dewaxed oil which was obtained had the following properties:

Gravity, API 34.7 Viscosity Index 132 Pour Point, F. 20 Color, ASTM -D 1500-1 1 The raffinate beforeextraction with furfural, formed sediment and lacquer upon exposure to air and an ultraviolet light source for less than 24 hours. The furfuralextracted dewaxed oil formed no sediment or lacquer when so exposed for at least 700 hours.

COMPARATIVE EXAMPLE A Opposed to the results shown in Examples 3 and 4 were those obtained with the same bottoms product which had been dewaxed With 60/40 MEK/toluene to a 20 F. pour point, but not extracted with furfural. The product darkened and formed sediment and lacquer in less than 24 hours in the ultraviolet light test and also when so exposed on the windowsill.

COMPARATIVE EXAMPLE B A portion of the dewaxed oil described in Example 1, was treated with percent by volume of furfural at 180 F. in a single stage. The extract comprised 1 percent by volume and the raffinate the balance. The color of the raflinate was L 2.5 in contrast to L 1.5 for the raffinate of Example 1. When tested in the ultraviolet light test, the raffinate formed lacquer and sediment in 17 hours.

COMPARATIVE EXAMPLE C Conventional antioxidants for lubricating oils have proven to be ineffective for stabilizing the foregoing oils which had not been treated with furfural. This is illustrated with an oil of the character of that described in Example 1, before treatment with furfural. One-tenth percent (0.1%) of 2,6-ditertiary butyl-4-methyl phenol Was incorporated in the oil. The resulting product was tested in the ultraviolet light test. There was no appreciable improvement as shown by a comparative test with the oil alone in the ultraviolet light test.

Having thus given a general description of the process and means of this invention and provided by way of example specific embodiments thereof, it is to be understood that no undue restrictions are to be imposed by reason thereof, and minor modifications may be made thereto without departing from the scope thereof.

What we claim is:

1. In a process for forming a lubricating oil resistant to deterioration upon exposure to light and air, from a high boiling hydrocarbon fraction, the improvement which comprises:

(a) hydrocracking said high boiling hydrocarbon fraction with a hydrocracking catalyst in the presence of hydrogen at elevated temperature and at elevated pressure to convert said fraction to a product containing from about 25 to about 50 volume percent boiling below about 650 F., said product comprising a plurality of fractions including a lubricating oil bottoms fraction boiling above about 650 F. and having a viscosity index of at least about said high boiling hydrocarbon fraction boiling above about 650 F. and being selected from the group consisting of a heavy gas oil, topped crude, residual stock, bright stock, cycle stock and mixtures thereof;

(b) separating said lubricating oil fraction from said plurality of fractions;

(c) extracting in a plurality of stages said lubricating oil fraction with furfural, to form a rafiinate and an extract, the extract comprising from about 0.5 to about 10 volume percent of the components of said lubricating fraction, and the raflinate having a vis cosity index substantially the same as the viscosity index of said lubricating oil fraction;

(d) and removing said furfural from said raffinate.

2. The process of claim 1 wherein said high boiling hydrocarbon fraction is a propane deasphalted rafiinate.

3. The process of claim 1 wherein said high boiling hydrocarbon fraction is a waxy fraction.

4. The process of claim 1 wherein said high boiling hydrocarbon fraction is a gas oil.

5. The process of claim 1 wherein the catalyst contact temperature is from about 600 F. to about 850 F.; and

hydrogen is circulated at a rate of from about 5000 to about 10,000 s.c.f. per barrel of charge of the high boiling hydrocarbon fraction.

6. The process of claim 1 wherein said lubricating oil fraction is so extracted with from about 30 to about 200 volume percent of said furfural.

7. The process of claim 1 wherein said lubricating oil fraction is so extracted with said furfural to remove from about 0.5 to about 5 volume percent of components of said lubricating oil fraction.

8. The process of claim 1 wherein the number of extraction stages is at least three,

References Cited UNITED STATES PATENTS Halter et al 20896 Holder et al. 208335 Fear 20896 Beuther et al. 208-19 Wilson et al. 20896 Kozlowski 208111 Egan et al. 20818 Campagne 20818 HERBERT LEVINE, Primary Examiner 

